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Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE. Dynamic Response of UAE Buildings Earthquakes. Dr. Jamal A. Abdalla , M. ASCE, M. EERI Associate Professor and Chair of Civil Engineering Department American University of Sharjah. Gulf Seismic Forum 2005

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Dynamic Response of UAE Buildings Earthquakes


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    1. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Dynamic Response of UAE Buildings Earthquakes Dr. Jamal A. Abdalla, M. ASCE, M. EERI Associate Professor and Chair of Civil Engineering Department American University of Sharjah

    2. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Outline • Geology, tectonics and seismicity of UAE • Seismic hazard assessment of UAE • Types of Buildings in UAE • Earthquake Resistant Design Provisions • Dynamic response of Villas to earthquakes • Results and discussions • Conclusionand Future Work

    3. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Geology of UAE • Geologically, the features of UAE follow that of the Arabian Platform • The rocks in the Arabian Platform accumulated on stable marine shelf • sandstones, siltstones, carbonates and salt basin characterize the region

    4. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Tectonics of UAE • Tectonically, UAE is situated in the South-Eastern part of the Arabian plate that is composed of sedimentary rocks that range in thickness from zero to 10 km, in addition to basalt and oceanic basin • There are several major fault systems that surround the Arabian Plate. • The northwest boundary of the Arabian Plate is the left-lateral Dead Sea Fault Zone. • The southeast boundary of the Arabian Plate is the Owen Fracture Zone (OFZ) in the northwestern Indian Ocean. • The western boundary of the Arabian Plate is the Red Sea Rift and Sheba Ridge systems. • The seismicity of few of these directly affects the seismicity of UAE. • The eastern boundry of the Arabian Plate is the Zagros Fold & Thrust Belt and Makran Subduction Zone which are the only two fault systems that have direct effect on UAE seismicity.

    5. Eurasian Plate Turkish Plate Zagros Fold Belt Dead Sea Fault Makran Subduction Arabian Plate African Plate Owen Fracture Zone Red Sea Fault Indian Plate Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Tectonics of UAE

    6. Iran Bahrain Arabian/Persian Gulf Qatar Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Gulf of Oman United Arab Emirates Sultanate of Oman Kingdom of Saudi Arabia Seismicity of UAE

    7. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Siesmic Hazard Assessment • The eastern portion of the Arabian Peninsula (UAE, Qatar, Bahrain, Kuwait, Northern Oman) were excluded from previous SHA studies • A seismic hazard assessment was conducted for UAE and its vicinity • The probabilistic approach, that takes into account the uncertainties in the level of earthquake magnitude, its hypocentral location, its recurrence relation and its attenuation relation is used

    8. Zone 3 Zone 2B Bahrain Iran Zone 2A Arabian/Persian Gulf Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Qatar Zone 1 Gulf of Oman United Arab Emirates Zone 0 Sultanate of Oman Kingdom of Saudi Arabia Seismic zoning map of UAE and its vicinity for 50 years period with 10% probability of being exceeded

    9. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Zone Factor (Z) • Large parts of UAE, specifically Southern UAE, lies within Zone 0 Greater Abu Dhabi area lies within Zone 1. • Fujaira, greater Dubai, Sharjah and Ajman area lies within Zone 2A. • No part of UAE lies within Zone 2B or Zone 3.

    10. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Factors affecting Dynamic Response of buildings • To design buildings to resist earthquake forces, several factors must be considered. Such factors can be divided into the following five categories: • seismological factors such as seismic zone on which the structure is to be constructed • geotechnical factors such as soil type, soil profile, soil dynamic properties and its liquefaction potential • structural factors such as lateral force resisting systems and dynamic properties of the buildings • architectural factors such as building shape and form • social factors such as building occupancy importance.

    11. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Analysis Methods • To include the earthquake ground motion effect, buildings can be analyzed using different static and dynamic methods. Such methods include: • Equivalent static method • Response spectrum method • Time history method • Push-over method. • For low and medium rise regular buildings in low and moderate seismic activity zones, the equivalent static method has been adopted predominately by almost all building codes. The equivalent static method formula is very much a function of similar factors.

    12. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Equivalent Static Method • The most widely used equivalent static method formula is that of the Uniform Building Code (UBC-94) adopted from SEAOC. This formula is the basis of most formulas found in other codes and it will be adopted here. • The equivalent static method calculates the lateral seismic base shear which is a function of many factors. • The base shear in a buildings can be calculated using the following formula (UBC-94): where: Z = Seismic zone factor; I = Importance factor; W = Weight of the building, total dead load and a percentage of live load; Rw= Numerical seismic coefficient (Response Modification Factor); C = Numerical coefficient.

    13. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Zone Factor (Z) • The Z-value represents the maximum effective peak acceleration (EPA) and is expressed as a fraction of the gravitational acceleration, g. The peak ground acceleration (PGA) are adjusted to give the effective peak acceleration EPA. The results are listed below

    14. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Spectral Acceleration Coefficient (C) • This coefficient is to account for the spectral amplification of ground motion based on structure fundamental period (T) and site response factor (S). The empirical formula for calculating fundamental period of vibration of buildings (in seconds) according to (UBC-94) is given by:

    15. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Other FactorsI and Rw • The importance factor, I, is determined based on the building importance and is used to provide for more conservative design for important facilities. The importance factor ranges from 1.0 for single family dwellings to 1.5 for building needed immediately after earthquake such hospitals, power stations and the like. • The response modification factor, Rw, is introduced to account for the reduction in structural response caused by damping of the structure and its inelastic response. The response modification factor ranges from 5 for masonry bearing wall system to 12 for dual systems with special-moment-resisting frame.

    16. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Types of Building in UAE • Concrete buildings are the dominant types of structural systems in UAE. • Modern single family residential buildings are predominately two story reinforced concrete buildings with a substantial set back in their third story. • Old houses are onestory reinforced concrete or masonry structures. • Industrial and commercial buildings range from three stories to 30 stories with the majority in the range of five to ten stories. • There are few steel structures which are mainly industrial hangers and warehouses.

    17. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Types of Building in UAE • Floor systems used on constructing buildings in UAE include slabs with beams, flat plate, hollow block slabs and occasionally waffle slabs and they can be modeled as rigid diaphragms. • Residential buildings are characterized by vertical geometric irregularities, mass irregularities and plan structural irregularities. • Most modern reinforced concrete buildings can be classified as ordinary moment resisting frames (OMRF) with fixed bases. • The commercial buildings usually have mezzanine wooden floors that can be modeled as flexible diaphragms and shear walls that classify them as dual systems.

    18. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Types of Building in UAE Commercial Building Apartment Building Single Family villa

    19. Near-Field Earthquake Characterized by: Large amplitudes Large frequency High velocity pulses Far-Field Earthquakes Characterized by: Small amplitudes Small frequency More consistent movements Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Near-Field vs Far-Field Earthquakes

    20. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acceleration Time History for Dibba Earthquake, October 21, 2004 East-West Direction

    21. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acceleration Time History for Dibba Earthquake, October 21, 2004 North-South Direction

    22. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acceleration Time History for Dibba Earthquake, October 21, 2004 Vertical Direction

    23. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acceleration Time History Recorded at AUS Station in Masafi, December 2002

    24. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acceleration Response Spectra (AUS Station in Masafi, December 2002)

    25. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Conclusions and Future Work • Three major elements of an earthquake design code, mainly seismic zoning, dynamic characteristics of common types of buildings and design response spectra were addressed in details and some recommendations were made. However, there are several factors that need to be specialized for UAE. In order to do so the following miles stones need to be achieved • Evaluation of relationship between buildings types, their width, their height and their fundamental period of vibration (T). • Determination of local site effect (S) and soil parameters for the common types of soils in UAE for amplification or attenuation of ground motion. • Development of design response spectra for areas of critical structures. • Evaluation of response modification factor (Rw) for buildings. • Evaluation of importance factors for buildings (I), elements, components and equipments. • Development of attenuation relationships for UAE to fine tune the seismic hazard map developed based on Zagros attenuation relation. • Study of the liquefaction potential of the different types of soils of UAE. • Installation of strong motion recorders (Seismometers) to record strong ground motion in different parts of the country and in major installations. • Instrumentation of critical and historical buildings and monitoring of their response. • Study earthquake codes of surrounding countries.

    26. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Acknowledgment The support for the research presented in this paper had been provided by the American University of Sharjah, Faculty Research Grant. Strong motion records are recorded by AUS Earthquake Observatory. This support is gratefully acknowledged. The views and conclusions are those of the author and should not be taken as those of the sponsor.

    27. Thank You

    28. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE EARTHQUAKE RESISTANT DESIGN CODES: BACKGROUND • The objectives of an earthquake resistant design code in general is to promote and protect the health, life and the economic well-being of the society in the event of severe and moderate earthquakes • Codes usually specify minimum standards for construction material, minimum strength for structural elements to prevent failure and maximum deformations or displacements (serviceability) to prevent excessive deflection, vibration and cracking. • Specification of structural detailing is usually given to ensure the desired ductile behavior of structural elements. • The code intention is to provide minimum probability of failure and largest probability of serviceability. • It is observed that engineered buildings are unlikely to experience structural damage or complete failure or collapse as the result of the effects of dead, live, or wind loads. However, in the event of severe earthquakes buildings are likely to behave in-elastically and the ultimate objective of the earthquake resistant design code is to prevent collapse of buildings while tolerating reasonable amount of structural damage.

    29. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE EARTHQUAKE RESISTANT DESIGN CODES: BACKGROUND • Almost all developed codes follow one the following pioneering code which are based on similar concept. • The pioneering code is the Uniform Building Code that is greatly influenced by the Structural Engineering Association of California (SEAOC) recommendations. • These recommendations have been adopted and embraced by many code developing agencies and organizations such as the National Earthquake Hazard Reduction Program (NEHRP), and later the International Building Code (ICC2000). • These codes had influenced many codes around the world. Other codes that have influenced are the Building Standard Law of Japan; Eurocode7and New Zealand Building Standard Law. • The above mentioned codes are predominately prescriptive codes which specify minimum strength and stiffness for structural members. There are new emerging Performance-Based Design (PBD) codes that have different philosophy than that of the prescriptive ones. Performance-based design codes permit the designer to meet certain standard performance objectives, independent of meeting the prescriptive strength and stiffness criteria. In other words quantifiable levels of damage for specified levels of hazard are permitted.

    30. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Earthquake Resistant Design Provisions • To design buildings to resist earthquake forces, several factors must be considered. Such factors can be divided into the following five categories: • seismological factors such as seismic zone on which the structure is to be constructed • geotechnical factors such as soil type, soil profile, soil dynamic properties and its liquefaction potential • structural factors such as lateral force resisting systems and dynamic properties of the buildings • architectural factors such as building shape and form • social factors such as building occupancy importance.

    31. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Analysis Methods • To include the earthquake ground motion effect, buildings can be analyzed using different static and dynamic methods. Such methods include: • Equivalent static method • Response spectrum method • Time history method • Push-over method. • For low and medium rise regular buildings in low and moderate seismic activity zones, the equivalent static method has been adopted predominately by almost all building codes. The equivalent static method formula is very much a function of similar factors.

    32. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Equivalent Static Method • The most widely used equivalent static method formula is that of the Uniform Building Code (UBC-94) adopted from SEAOC. This formula is the basis of most formulas found in other codes and it will be adopted here. The equivalent static method calculates the lateral seismic base shear which is a function of the factors mentioned above. The base shear in a building can be calculated using the following formula (UBC-94): where: Z = Seismic zone factor; I = Importance factor; W = Weight of the building, total dead load and a percentage of live load; Rw = Numerical seismic coefficient (Response Modification Factor); C = Numerical coefficient determined.

    33. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Siesmic Hazard Assessment • Seismic hazard zoning studies were conducted for different countries of the Arabian Peninsula • The eastern portion of the Arabian Peninsula (UAE, Qatar, Bahrain, Kuwait, Northern Oman) were excluded from previous SHA studies • Some extrapolated result shows hazard levels of almost 0.5g at the northern most part of the UAE. This result is very high and unrealistic. • This study is intended to include UAE and its surrounding areas and improves on previous extrapolated SHA result.

    34. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic hazard assessment • There are two prevalent methods for seismic hazard analysis; the deterministic approach and the probabilistic approach • The probabilistic approach, used in this investigation, takes into account the uncertainties in the level of magnitude of earthquake, its hypocentral location, its recurrence relation and its attenuation relation

    35. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Steps of the Probabilistic Seismic Hazard The steps for seismic hazard assessment can be summarized as follows: • Modeling of seismic source regions; • Evaluation of recurrence relation, i.e., frequency-magnitude relation; • Evaluation of attenuation laws for intensity or peak ground acceleration; • Evaluation of activity rate for earthquake-probability of occurrence; • Evaluation of basic parameters such as lower and upper bound for earthquake magnitude and distribution of seismic events and • Evaluation of local site effects such as soil type, geotechnical characteristics of sediments, topographic effects, etc.

    36. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Modeling of seismic source regions The seismic source regions are: • Source Region I: Main Zagros Thrust Region. • Source Region II: North East Arabian Gulf Region. • Source Region III: Northern Emirates Region • Source Region IV: Lut Region • Source Region V: Central Iran Region. • Source Region VI: Makran Region. • Source Region VII: South East Arabian Gulf Region

    37. Region V Region I Region II Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Region IV Bahrain Region III Iran Qatar Region VI Arabian/Persian Gulf Region VII Gulf of Oman United Arab Emirates Sultanate of Oman Kingdom of Saudi Arabia Seismic source regions of UAE and its surrounding (for M≥4 from 1964-2002 and for M≥6 from 1900-1964)

    38. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Recurrence and Attenuation Relations • Gutenberg and Richter had devised this logarithmic relationship (G-R formula) for seismic hazard analysis • An attenuation relation that resulted from calibration and adjustment of constants to reflect the region characteristics such as transmission path, soil type, source, etc., developed by IIEES [Zare, 2002] is used in the current study. The general form of the attenuation equation is in the following form:

    39. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Hazard Parameters

    40. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Hazard Results • Seismic Hazard Analysis for three time spans has been conducted • Mainly, 50, 100 and 200 years • Seismic zone map for 475 years return period is generated

    41. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Iran Bahrain Arabian/Persian Gulf Qatar Gulf of Oman United Arab Emirates Kingdom of Saudi Arabia Sultanate of Oman PGA ( ) for 50 years time span

    42. Iran Bahrain Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Arabian/Persian Gulf Qatar Gulf of Oman United Arab Emirates Sultanate of Oman Kingdom of Saudi Arabia PGA ( ) for 100 years time span

    43. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Iran Bahrain Arabian/Persian Gulf Qatar Gulf of Oman United Arab Emirates Kingdom of Saudi Arabia Sultanate of Oman PGA ( ) for 200 years time span

    44. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Summary of PGA (in g) with a 10% probability of being exceeded in time span

    45. Zone 3 Zone 2B Bahrain Iran Zone 2A Arabian/Persian Gulf Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Qatar Zone 1 Gulf of Oman United Arab Emirates Zone 0 Sultanate of Oman Kingdom of Saudi Arabia Seismic zoning map of UAE and its vicinity for 50 years period with 10% probability of being exceeded

    46. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Zone factor (Z) • The Z-value represents the maximum effective peak acceleration (EPA) and is expressed as a fraction of the gravitational acceleration, g. The peak ground acceleration (PGA) in Table 1 need to be adjusted to give the effective peak acceleration EPA. The results are listed below

    47. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Seismic Zone Factor (Z) Large parts of UAE, specifically Southern UAE, lies within Zone Zero Greater Abu Dhabi area lies within Zone 1. Fujaira, greater Dubai, Sharjah and Ajman area lies within Zone 2A. No part of UAE lies within Zone 2B or Zone 3.

    48. Gulf Seismic Forum 2005 February 20-23, 2005, Al-Ain, UAE Spectral Acceleration Coefficient (C) • This coefficient is to account for the spectral amplification of ground motion based on structure fundamental period (T) and site response factor (S). The empirical formula for calculating fundamental period of vibration of buildings (in seconds) according to (UBC-94) is given by: